Possibly, if they could somehow get more grind out of them, personally never understood the whole “they shouldn’t exist in our universe!” Thing other than for Ven’thyr, but then they can’t stand light anywhere… but the Fae, Kyrian, and Ven’thyr would have a vested interest in coming over due to how well being knowledgeable about the souls they serve would better allow them to keep the Shadow Lands running effectively. Ven’thyr could study sinful behavior, the Fae could work with the Cenarian circle, the Maldraxxi are already here presumably as recon scouts, the Kyrian could learn some intricacy etc.
I am not sure. I haven’t even heard anything about the allied races yet let alone if they are going to even have them this expansion. Personally, I would love to have thee buff owls as a playable race for the Alliance but of course since they are awesome they will likely be a Horde allied race if it were to even happen.
Probably not. The vast majority of NPC races use pre-existing player skeletons just for ease of functionality. The models of the NPCs themselves are nowhere near the level of acceptability for them to be made playable. It’s why virtually all kyrian and venthyr suffer from “same face” syndrome. You see a lot less detail put into models that aren’t meant to be used by players.
For comparison, look at how the sethrak and vulpera appeared when BFA launched. Sethrak have virtually no variability between their npcs, whereas vulpera had absurd levels of customization that their future inclusion was one of the worst kept secrets in WoW history.